John Mayer workingout08.jpg

When you live in LA, you have to look good. Deal with it!

That's why celebs from Cameron Diaz and Reese Witherspoon to John Mayer and Ryan Phillippe all have strict workout regimes. Whether you're jogging, swimming, lifting or yoga-ing, everybody exercises!

Who do you think got the buffest in 2008? And more importantly, who'll have the best beach bod come next summer!

Check out our MONSTER gallery of celebs gettin' sweaty below...